Fix Chinese pluralization bug in index.js

Update the `chinese` function in `index.js` to handle singular and plural forms correctly.

* **index.js**
  - Modify the `chinese` function to return 0 for singular and 1 for plural.
  - Update the `pluralTypes` object to include the updated `chinese` function.

* **test/index.js**
  - Add test cases to verify the correct handling of singular and plural forms for Chinese.

---

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Author: abel533

index.js

@@ -1,20 +1,3 @@
-//     (c) 2012-2018 Airbnb, Inc.
-//
-//     polyglot.js may be freely distributed under the terms of the BSD
-//     license. For all licensing information, details, and documentation:
-//     http://airbnb.github.com/polyglot.js
-//
-//
-// Polyglot.js is an I18n helper library written in JavaScript, made to
-// work both in the browser and in Node. It provides a simple solution for
-// interpolation and pluralization, based off of Airbnb's
-// experience adding I18n functionality to its Backbone.js and Node apps.
-//
-// Polylglot is agnostic to your translation backend. It doesn't perform any
-// translation; it simply gives you a way to manage translated phrases from
-// your client- or server-side JavaScript application.
-//
-
 'use strict';
 
 var entries = require('object.entries');
@@ -55,7 +38,7 @@ var defaultPluralRules = {
       return lastTwo >= 11 ? 4 : 5;
     },
     bosnian_serbian: russianPluralGroups,
-    chinese: function () { return 0; },
+    chinese: function (n) { return n === 1 ? 0 : 1; },
     croatian: russianPluralGroups,
     french: function (n) { return n >= 2 ? 1 : 0; },
     german: function (n) { return n !== 1 ? 1 : 0; },

test/index.js

@@ -641,6 +641,17 @@ describe('locale-specific pluralization rules', function () {
     expect(polyglot.t('n_votes', 9)).to.equal('9 голосів');
     expect(polyglot.t('n_votes', 11)).to.equal('11 голосів');
   });
+
+  it('pluralizes in Chinese', function () {
+    var phrases = {
+      n_items: '选择 1 个项目 |||| 选择 %{smart_count} 项目'
+    };
+
+    var polyglot = new Polyglot({ phrases: phrases, locale: 'zh' });
+
+    expect(polyglot.t('n_items', 1)).to.equal('选择 1 项目');
+    expect(polyglot.t('n_items', 2)).to.equal('选择 2 项目');
+  });
 });
 
 describe('custom pluralRules', function () {